The present invention relates to a ventilation device for a combined spring accumulator and operating brake cylinder of a vehicle.
A ventilation device of the general type under consideration is described in DE 102 28 934 A1.
If the spring-actuated brake cylinder of a combined spring accumulator and operating brake cylinder is actuated by depressurization of its pressurized-fluid chamber, the spring chamber becomes larger because of the resulting extension of the spring and displacement of the piston. To ensure that reduced pressure that would prevent delivery of the spring force does not occur in the spring chamber while it is becoming larger, the spring chamber is in communication with the pressurized-fluid chamber of the operating brake cylinder via a pressure-controlled valve device functioning as a ventilation device.
Because the compressed air supplied to the pressurized-fluid chamber of the spring-actuated brake cylinder and to the pressurized-fluid chamber of the operating brake cylinder is cleaned and dried in the upstream compressed-air intake and conditioning system, the risk of corrosion and fouling in the region of the spring chamber and at the spring is decisively reduced by this type of ventilation.
The known ventilation device uses a pressure-controlled valve which has two working ports and one control port as well as a valve piston that can move in the direction of the longitudinal axis of the valve. Depending on whether the pressurized-fluid chamber of the operating brake cylinder and/or the pressurized-fluid chamber of the spring-actuated brake cylinder is or are vented or pressurized with compressed air, and depending on the position in which the piston of the spring-actuated brake cylinder is located, the two working ports of the valve, and, thus, also the spring chamber of the spring-actuated brake cylinder and the pressurized-fluid chamber of the operating brake cylinder, are in communication with one another or shut off from one another.
In the pressure-controlled valve of the known ventilation device, the two working ports and the control port are disposed on the valve in such a way that they run perpendicular to the longitudinal axis of the valve piston. When the pressure-controlled valve is in its open position, the air flows from the chamber containing the higher pressure—either the spring chamber of the spring-actuated brake cylinder or the pressurized-fluid chamber of the operating brake cylinder—via the one working port associated with that chamber to the respective other working port, which is associated with the chamber containing the lower pressure. In the process, the air flow is deflected several times in the valve.